Why is sunscreen a threat to coral reefs?

Oxybenzone, a common UV-filtering agent in sunscreens, linked to deformities and DNA damage in coral around the world.

Coral reefs are extremely susceptible to a chemical found in the most common sunscreens.
(Photo: Jolanta Wojcicka/Shutterstock)

Is the sunscreen you're about to lather on coral reef-friendly?

That's the question marine scientists are hoping people will ask themselves in the future before jumping in to explore one of the ocean's great wonders. An international team of researchers, including those from the U.S. National Aquarium and NOAA, discovered a troubling link between a common ingredient in sunscreens and die-off in coral reefs, and they published those findings in 2015.

The chemical oxybenzone, a UV-filtering compound, has been found to be extremely toxic to coral. And it doesn't take much: As little as one drop in a volume of water larger than 6.5 Olympic-sized swimming pools is potent enough to cause damage.

"The use of oxybenzone-containing products needs to be seriously deliberated in islands and areas where coral reef conservation is a critical issue," team leader Craig Downs of the Haereticus Environmental Laboratory in Virginia told Phys.org. "We have lost at least 80 percent of the coral reefs in the Caribbean. Any small effort to reduce oxybenzone pollution could mean that a coral reef survives a long, hot summer, or that a degraded area recovers."

According to the published study, oxybenzone exposure can lead to DNA damage and "coral bleaching," which robs reefs of valuable algae and nutrition. Young coral larvae, however, seem the suffer the worst fate, with the chemical effectively "trapping them in their own skeleton," and rendering them unable to float away and establish new colonies.

More than just coral at risk

Following up the 2015 research, Downs is now looking more closely at sunscreen's impact on marine life, not just coral. The research team is also looking for sunscreen in marine animal tissue. While the findings won't be published until late 2017, Downs did share some of the broad strokes with Oceans Deeply, including the threat posed by aerosol sunscreen particles landing on the sand as we spray it on, and that sand getting washed out to sea. Those particles pose a threat to not only animals that rely on the sand for nesting — i.e., sea turtles — but underwater coral, starfish and urchins, too.

"We knew oxybenzone was a sexual endocrine disruptor from the science of it on fish and mammals, but the skeleton disruption in corals was completely unexpected," Downs told Oceans Deeply.

Downs ranks oxybenzone and other chemicals like pesticides and those leaked from plastics as the third most pressing threat to coral reefs, after sewage and fertilizer pollution and, of course, climate change.

How to save your skin and the coral reefs

While the varieties of sunscreens that contain natural and nontoxic ingredients has risen in recent years, the researchers say oxybenzone is still a primary component of some 3,500 sunscreen products worldwide. Indeed, the most recent report from the Environmental Working Group analyzing 1,500 sunscreen products found 75 percent as either ineffective or containing ingredients harmful to your health. The chemical they singled out? None other than oxybenzone.

So what can you do to avoid skin cancer but also not harm one of the planet's most vital ecosystems? The EWG has a list of 242 sunscreens, lip balms and moisturizers that do not contain oxybenzone or other worrisome ingredients. Wearing clothing and hats with UV-filtering properties can also offer protection independent of chemical sunscreens.

"Wear rash guards or scuba wetsuits and skip all the hygienic products when you go diving," John Fauth of the University of Central Florida told Phys.org. "If we could do it for a week at a time, people can certainly forgo it for a few hours to help protect these reefs for our children and their children to see."

This story was originally published October 2015 and has been updated with new information.